Chest CT May Help Diagnose COVID-19 in Early Stages

A new study suggests that patients with negative RT-PCR tests who are suspected of having COVID-19 may benefit from chest computed tomography (CT), which could help identify early stages of the disease.

Chest computed tomography (CT) could be beneficial along with RT-PCR testing in diagnosing COVID-19 for patients in whom the disease is suspected, according to a recently published study.

In the retrospective study, published in Clinical Imaging, researchers noted that chest CT revealed lung involvement in over 98 percent of 569 patients admitted to the emergency department of a university hospital in Istanbul, Turkey in a three-month period between March and June 2020. However, slightly over 50 percent of the patients (285) in the study tested negative for SARS-CoV-2 infection on real-time reverse transcription polymerase chain reaction (RT-PCR) tests.

“Chest CT is essential in COVID-19 but with low dose radiation. We need a more accurate and rapid test than RT-PCR for SARS-CoV-2,” emphasized Dr. Müfide Arzu Özkarafakılı, who was the lead author of the study and is affiliated with the Department of Chest Diseases at Sisli Hamidiye Etfal Training and Research Hospital and the University of Health Sciences in Istanbul, Turkey.

Ground-glass opacity (GGO) was the most common radiological finding, reported in 539 (97.2 percent) cases, followed by consolidation in 365 patients (64.1 percent), and crazy paving interlobular septal thickening in 160 patients (28.1 percent). The mean COVID-19 Reporting and Data System (CO-RADS) score was 5.4 ± 0.7. Developed by Dutch radiologists, CO-RADS categorizes the level of suspicion of COVID-19 pneumonia from 0 to 6.

“We interpreted this finding such that the RT-PCR negative cases are still at an early stage,” the study authors wrote. “GGO are early stage (0-4 days) findings in COVID-19 pneumonia, where vascular boundaries cannot be selected, where air gaps are filled with fluid, blood or pus, and they tend to be multifocal, peripheral, subpleural and bilateral.”

The distribution of lesions on CT were largely bilateral (544 patients, 95.6 percent) and multilobar (553 patients, 97.2 percent) along with 14 unilateral lesions (2.5 percent) and five unilobar lesions (0.9 percent), according to the study. The study authors said localization of lesions was peripheral (557 patients, 97.8 percent), posterior (151 patients, 26.5 percent) and central (33 patients, 5.8 percent).

“CT plays an essential role for diagnosis, isolation and treatment in cases of COVID-19, and RT-PCR negative test should be verified by CT,” the study authors concluded.

Chest CT could help overcome some of the weaknesses of RT-PCR tests, which include time for the test to conclude, sampling errors and inadequate nasopharyngeal samples, according to the study.

The study authors noted limitations, including a lack of examination of repeated RT-PCR results and dynamic changes in chest CT, and the time between onset of symptoms and testing being unclear. They also acknowledge that the Fleischner Society recommends CT regardless of the RT-PCR result in moderate to severe cases, but not in mild or asymptomatic cases.

Previous research has shown a 97 percent sensitivity of chest CT compared with 60 to 70 percent for RT-PCR. A recent study in China, published in the American Journal of Roentgenology, found that lower levels of pulmonary consolidation on chest CT indicate earlier disease among patients who initially tested negative for COVID-19.